You'll be governed by JAR FCL
JAR-FCL 3.040 (pertains to Class1)
(3) being pregnant, shall inform the
Authority in writing of such injury or pregnancy,
and as soon as the period of 21 days has elapsed
in the case of illness. The medical certificate
shall be deemed to be suspended upon the
occurrence of such injury or the elapse of such
period of illness or the confirmation of the
pregnancy,
5)
in the case of pregnancy, the
suspension may be lifted by the Authority for
such period and subject to such conditions as it
thinks fit (see JAR–FCL 3.195(c) and 3.315(c)
and shall cease upon the holder being medically
examined under arrangements made by the
Authority after the pregnancy has ended and
being pronounced fit to resume her functions as
a member of the flight crew.
JAR–FCL 3.195 Gynaecology and
obstetrics
(a) An applicant for or the holder of a Class 1
medical certificate shall not possess any functional
or structural obstetric or gynaecological condition
which is likely to interfere with the safe exercise of
the privileges of the applicable licence(s).
(b) An applicant with a history of severe
menstrual disturbances unamenable to treatment
shall be assessed as unfit.
(c)
Pregnancy entails unfitness. If obstetric
evaluation indicates a completely normal
pregnancy, the applicant may be assessed as fit
until the end of the 26th week of gestation, in
accordance with paragraph 1 Appendix 8 to Subpart
B. Licence privileges may be resumed upon
satisfactory confirmation of full recovery following
confinement or termination of pregnancy.
(d) An applicant who has undergone a major
gynaecological operation shall be assessed as unfit
for a minimum period of three months and until
such time as the effects of the operation are not
likely to interfere with the safe exercise of the
privileges of the licence(s) (see paragraph 2
Appendix 8 to Subpart B).
Source
JAR FCL 3
So that's the law. you can't fly once pregnancy is confirmed. You can fly after that untill the 26th week so long as every thing is fine. You can't decide that, your doctors will.
If you are in a small company I would discuss it with them first. ie find out when the quiet times are and plan your pregnancy that way. Take all your leave then or unpaid leave as well as the maternity leave you should be owed.
You may not be able to fly but you're not "sick" in the classic sense. See if you can teach recurrent courses such as CRM or help out in crewing/ops. They're usually understaffed.
Good luck.